The growing ubiquity of mobile computing devices, and reliance upon them, means that losing them is simultaneously more likely and more damaging. For example, the annual CSI/FBI Computer Crime and Security Survey ranks laptop and mobile device theft as a prevalent and expensive problem for corporations. To help combat this growing problem, corporations and individuals are deploying commercial device-tracking software, for example, “LoJack for Laptops” on their mobile devices. These systems typically send the identity of the device and its current network location (e.g., its IP address) over the Internet to a central server run by the device-tracking service. After losing a device, the service can determine the location of the device and, subsequently, can work with the owner and legal authorities to recover the device itself The number of companies offering such services attests to the large and growing market for device tracking.
Unfortunately, these systems are incompatible with the oft-cited goal of location privacy, since the device-tracking services can always monitor the location of an Internet-enabled device—even while the device is in its owner's possession. This presents a significant barrier to the psychological acceptability of tracking services. To paraphrase one industry representative: companies will deploy these systems in order to track their devices, but they won't like it. The current situation leaves users of mobile devices in the awkward position of either using tracking services or protecting their location privacy.
An alternative is offered known as privacy-preserving device-tracking systems. Such a system should provide strong guarantees of location privacy for the device owner's legitimately visited locations while nevertheless enabling tracking of the device after it goes missing. It should do so even while relying on untrusted third party services to store tracking updates. It would also be desirable to log forensic information, while preserving privacy. As used herein, the term “forensic information” can refer to any information that can be useful in a legal action, such as prosecuting a person who is accused of stealing an electronic device, or for gathering evidence. For example, forensic information might include tracking information showing where an electronic device has been moved after it was stolen, or photos, video, audio, and other types of sensor data that were logged after the device was stolen. It would be desirable to provide such forensic information to assist in locating a stolen device, since photos or videos of a person or even of an environment proximate to a stolen device could be useful in determining where the device is located and for establishing the identity of the person or persons in the proximity of the device after it has gone missing.